1. Technical Field
The present invention relates to electro-optic devices, and particularly to an electro-optic device including a pixel section disposed in the middle region and a terminal section through which another semiconductor circuit or another wiring board is mounted in the outer region of the electro-optic device.
2. Related Art
In electro-optic devices such as liquid crystal display devices, a pixel section displaying images is disposed in the middle region, and a circuit for driving the pixel section is disposed in the pixel section. If the driving circuit is large or operates at a high speed, and accordingly requires the use of another semiconductor circuit or a semiconductor circuit mounted on another wiring board, a terminal section is provided in the outer region of the electro-optic device and the additional semiconductor circuit or wiring board is mounted through the terminal section.
When the pixel section is disposed in the middle region and the terminal section is provided in the outer region, it is preferable that the formations of the pixel section and the terminal section are performed in one step.
For example, JP-A-2006-309028 discloses a method for forming a terminal section suitable for the COG (Chip On Glass) technique in display devices or the like. In this disclosure, the molybdenum gate electrodes of the pixel section and the molybdenum wires of the terminal section are formed in the same step, and data lines of the pixel section and connection wires of the terminal section are formed in the same step. After a protective film and a planarizing film are formed over the entire surface, the planarizing layer is removed from the regions overlying the data lines of the pixel section and the regions in the terminal section outside the ends of the data lines in the same step. Also, a relatively wide area of the protective film is removed from the terminal section in the same step as the contact holes are formed in the protective film in the pixel section. In the pixel section, a transparent electroconductive film connected to the contact holes is formed over the planarizing layer to form pixel electrodes. In the terminal section, the transparent electroconductive film is formed over the connection wires, and the COG technique is applied to the transparent electroconductive film. The data line and the connection wire have a multilayer structure of molybdenum/aluminum/molybdenum or titanium/aluminum/titanium. The protective film is made of SixNy (silicon nitride). The planarizing layer is made of an acrylic resin. The transparent electroconductive film is made of ITO (indium tin oxide) or IZO (indium zinc oxide). The terminal section also uses ITO or IZO. This is because ITO and IZO can prevent the terminal section from corroding and an oxide coating from being formed over the surface of the terminal section, in the manufacturing process of the display device from the step of forming the terminal section to the step of COG mounting, and because the use of ITO or IZO allows the COG mounting technique to establish good electric connection and ensures the reliability of the product after COG mounting.
In JP-A-2006-309028, the molybdenum wires, the molybdenum/aluminum/molybdenum or titanium/aluminum/titanium multilayer structure and the transparent electroconductive film that are formed in the pixel section are also used for the terminal section.
Although in this document, the connection wires, or connection wire layer, have a molybdenum-containing structure or a titanium-containing structure, these structures each have merits and demerits. More specifically, the molybdenum-containing structure is easily formed by wet etching and the surface coating formed in the atmosphere is an oxide or a hydroxide film, which can be easily removed with water or the like. However, it is not easily formed by dry etching and is accordingly difficult to form fine. On the other hand, the titanium-containing structure can be formed by dry etching and is accordingly suitable to form a fine structure. However, it is liable to be oxidized. For example, if an ITO layer is formed on the titanium-containing structure, an oxide coating is formed in its atmosphere to increase the interface resistance.
When fine wires and a fine terminal section are formed, the SixNy protective film is also formed in a desired shape by dry etching using a fluorine-containing gas as in JP-A-2006-309028. In this instance, a product of reactive components including fluorine is formed over the surface of the connection wires. If the connection wires have the molybdenum-containing structure, the surface product can be removed together with the molybdenum hydroxide coating by cleaning with water or the like. If the connection wires have the titanium-containing structure, however, the surface product cannot be removed only by simply cleaning with water.
In order to form fine wires and a fine terminal section, the connection wire preferably has a titanium-containing structure. However, the interface resistance between the connection wire of the terminal section and the ITO layer is disadvantageously increased and the surface product is difficult to remove, as described above.